{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-90071", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-90071" ], "published": "2026-09-17T16:10:40Z", "summary": "net/sched: sch_teql: restore skb->dev on the slave failure path", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_teql: restore skb->dev on the slave failure path\n\nteql_master_xmit() sets skb->dev = slave before calling the slave's\nndo_start_xmit(), but never restores it when that transmit fails. The\nskb then walks on to the next slave still pointing at the previous one.\n\nIf a later slave has no resolved neighbour, teql_resolve() hands the skb\nto neigh_event_send(), which queues it on that neighbour's arp_queue\nwith the stale skb->dev. skb->dev holds no reference, so deleting the\nprevious slave frees the net_device while the skb is still queued.\nWhatever runs next on that skb - arp_error_report() on timeout, or\nneigh_direct_output() -> dev_queue_xmit() once the neighbour resolves -\ncauses a UAF like the one below:\n\nBUG: KASAN: slab-use-after-free in __icmp_send (net/ipv4/icmp.c:914 (discriminator 2))\nRead of size 4 at addr ffff888106e100b0 by task flood_packet/527\nCPU: 0 UID: 0 PID: 527 Comm: flood_packet Not tainted 7.2.0-rc6-g594d90519502 #1 PREEMPT(lazy)\nHardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\nCall Trace:\n\ndump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)\nprint_report (mm/kasan/report.c:378 mm/kasan/report.c:482)\n? __pfx__raw_spin_lock_irqsave (./include/asm-generic/qrwlock.h:122 (discriminator 4))\n? __icmp_send (net/ipv4/icmp.c:914 (discriminator 2))\nkasan_report (mm/kasan/report.c:595)\n? __icmp_send (net/ipv4/icmp.c:914 (discriminator 2))\n__icmp_send (net/ipv4/icmp.c:914 (discriminator 2))\n[...]\nipv4_link_failure (net/ipv4/route.c:1251 net/ipv4/route.c:1258)\n? __pfx_ipv4_link_failure (./include/linux/skbuff.h:4327)\n? _raw_write_lock (./include/linux/instrumented.h:55 ./include/linux/atomic/atomic-instrumented.h:1301 ./include/asm-generic/qrwlock.h:98 ./include/linux/rwlock_api_smp.h:230 kernel/locking/spinlock.c:304)\n? __pfx__raw_write_lock (kernel/locking/spinlock.c:175)\narp_error_report (./include/net/dst.h:438 net/ipv4/arp.c:296)\nneigh_invalidate (net/core/neighbour.c:1077)\nneigh_timer_handler (net/core/neighbour.c:1169)\n[...]\nAllocated by task 505:\nkasan_save_stack (mm/kasan/common.c:57)\nkasan_save_track (mm/kasan/common.c:78)\n__kasan_kmalloc (mm/kasan/common.c:398 mm/kasan/common.c:415)\n__kvmalloc_node_noprof (./include/linux/kasan.h:263 mm/slub.c:5334 mm/slub.c:6905)\nalloc_netdev_mqs (net/core/dev.c:12055 (discriminator 2))\nrtnl_create_link (net/core/rtnetlink.c:3721)\nrtnl_newlink (net/core/rtnetlink.c:3903 net/core/rtnetlink.c:4044 net/core/rtnetlink.c:4159)\nrtnetlink_rcv_msg (net/core/rtnetlink.c:7076)\n[...]\nFreed by task 536:\nkasan_save_stack (mm/kasan/common.c:57)\nkasan_save_track (mm/kasan/common.c:78)\nkasan_save_free_info (mm/kasan/generic.c:584)\n__kasan_slab_free (mm/kasan/common.c:253 mm/kasan/common.c:285)\nkfree (./include/linux/kasan.h:235 mm/slub.c:2677 mm/slub.c:6377 mm/slub.c:6692)\ndevice_release (drivers/base/core.c:2636)\nkobject_put (lib/kobject.c:689 lib/kobject.c:720 ./include/linux/kref.h:65 lib/kobject.c:737)\nnetdev_run_todo (net/core/dev.c:11756)\nrtnl_dellink (net/core/rtnetlink.c:157 ./include/linux/rtnetlink.h:135 net/core/rtnetlink.c:3651)\nrtnetlink_rcv_msg (net/core/rtnetlink.c:7076)\n[...]\n\nFix this by restoring skb->dev to the master at the end of each slave's\niteration.", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.12.87-1+rpt1~bookworm", "1:6.12.93-1+rpt1", "1:6.12.96-1+rpt1", "1:6.12.109-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.12.87+rpt-rpi-2712", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v6", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v7", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v7l", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v8", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { 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"binary_version": "1:6.18.50-1+rpt1" }, { "binary_name": "linux-image-6.18.50+rpt-rpi-v8-rt", "binary_version": "1:6.18.50-1+rpt1" } ] }, "database_specific": { "per_version": { "1:6.18.29-1+rpt1": { "linux_commit": "66318c5b5cd8145a662303af12ed39ac07eb27cc", "upstream_version": "6.18.29", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.52" }, "1:6.18.33-1+rpt1": { "linux_commit": "95b85bebbedcaedfa7ca79116ed38b7376fba412", "upstream_version": "6.18.33", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.52" }, "1:6.18.34-1+rpt1": { "linux_commit": "c8c7494100e99ee05b11aaa4f0588a223a63d1af", "upstream_version": "6.18.34", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.52" }, "1:6.18.39-1+rpt1": { "linux_commit": "60ea684a8ace97bb0db1a16e20753bdd6ab371ff", "upstream_version": "6.18.39", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.52" }, "1:6.18.50-1+rpt1": { "linux_commit": "cff533aec2fa601846766b32ff57204e0a61bed7", "upstream_version": "6.18.50", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.52" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-90071" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/1360bc93f5be1be3cf937ebea667b3418dd30a79" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/d453bf439ef230b5743afc25e194adacca8c6e43" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/012559cf3c67ce8825a31d4f66b040b6fbaf775e" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/aa39a790d56b40bfcf3861653ceb46a3a113adb6" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/00d8a387b23b7831ad9919256a6b9caaa10f19c3" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/96bc345a3f17543d0d92ada609e02198d6380e26" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/0cd75037948567193f7f5767176538822ce23873" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/dc4b95b8fee95113587e93ca116356032d271371" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-09-18T17:55:42Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.8, "cvss_v3_severity": "High", "scenario": "AV:L - teql_master_xmit() itself writes skb->dev to the slave, and the UAF is completed by a local RTM_DELLINK (rtnl_dellink \u2192 netdev_run_todo) of that slave while the skb sits on another slave's arp_queue; the packet reaches teql_master_xmit via sendto/udp_sendmsg \u2192 ip_finish_output2 \u2192 __dev_queue_xmit on teql0, not via a remote protocol field.\nAC:L - The attacker chooses the slaves, sends on teql0 so teql_master_xmit() leaves skb->dev on a failed ndo_start_xmit/netif_xmit_frozen_or_stopped slave, then teql_resolve()/neigh_event_send() queues that skb for an unresolved neighbour, then issues RTM_DELLINK; flood_packet plus an unanswered ARP destination make this repeatable without third-party timing.\nPR:L - RTM_NEWLINK, RTM_NEWQDISC (tc_modify_qdisc \u2192 teql_qdisc_init) and the freeing RTM_DELLINK all go through rtnetlink_rcv_msg(), which requires netlink_net_capable(skb, CAP_NET_ADMIN) against sock_net(skb->sk)->user_ns; unshare -Urn grants that namespaced capability without init-namespace root.\nUI:N - The attacker alone creates the slaves, grafts the teql0 qdisc, injects packets into teql_master_xmit(), and deletes the stale skb->dev slave with RTM_DELLINK; no other user must open a file, mount a volume, or otherwise act.\nS:U - The freed object is a kernel net_device from alloc_netdev_mqs()/rtnl_newlink, used later on the same host via skb->dev in __icmp_send() or dev_queue_xmit(); this is in-kernel memory corruption, not a VM, IOMMU, or hypervisor boundary crossing.\nC:H - KASAN reports a slab-use-after-free read of the freed net_device in __icmp_send() (skb_in->dev->flags) from arp_error_report(); the same dangling skb->dev is consumed by neigh_direct_output() \u2192 dev_queue_xmit(), and reclaim of that slab object yields an arbitrary kernel read.\nI:H - Once the neighbour resolves, neigh_update_process_arp_queue() calls neigh_direct_output() \u2192 dev_queue_xmit() on the dangling skb->dev, so a reclaimed net_device's netdev_ops (ndo_start_xmit) become attacker-controlled, giving an arbitrary kernel write and control-flow hijack.\nA:H - The reported path is neigh_timer_handler() \u2192 neigh_invalidate() \u2192 arp_error_report() \u2192 ipv4_link_failure() \u2192 __icmp_send() hitting a KASAN slab-use-after-free of the deleted slave net_device, which oopses/panics the kernel even without further exploitation." } } }